Propeller mechanism for boats



March 2, 1965 K. A. BERGSTEDT 3,171,382

PROPELLER MECHANISM FOR BOATS Filed Oct. 17, 1962 2 Sheets-Sheet 1 IN VENTOR 8& j J

Man]! 2, 1965 K. A. BERGSTEDT 3,171,382

PROPELLEIR MECHANISM FOR BOATS Filed Oct. 1'7, 1962 2 Sheets-Sheet 2 INVENTOR.

. f @w mzcwdww 4 United States Patent 3,171,382 PROPELLER MECHANISM FOR BOATS Karl Abdon Bergstcdt, Goteborg, Sweden, assignor to AB Volvo-Penta, Goteborg, Sweden, a corporation of Sweden Filed Oct. 17, 1962, Ser. No. 231,122 Claims priority, application Sweden, Get. 24, 1961, 10,548/61 Claims. (Cl. 115-34) This invention relates to a propeller mechanism for boats of the type in which steering is effected by turning the propeller about a substantially vertical axis. Such mechanisms are used for example in connection with inboard motors where the shaft of the motor passes horizontally outwards through the stern board to a gear case from which a vertical driving shaft transmits the motor power to the propeller. The vertical driving shaft as well as the propeller and its shaft are mounted in a turnable propeller housing. In a mechanism of this kind a torque arises which tends to turn the propeller housing with the result that the boat will proceed along a curved path when the rudder is released. Consequently, the torque must be compensated for by bearing permanently on the rudder, this being an inconvenient and fatiguing operation.

The object of this invention is to eliminate this inconvenience by an improved propeller mechanism a suitable embodiment of which is described hereinbelow with reference to the annexed drawing in which:

FIG. 1 is a lateral elevation of the improved propeller mechanism mounted on the stern board of a boat,

FIG. 2 a cross sectional view of the propeller housing along the line IIII in FIG. 1,

FIG. 2A a view similar to FIG. 2 showing a cam profile of spiral (helical) form;

FIG. 3 a partially sectional rear view of the mechanism, and

FIG. 4 a longitudinal sectional View of an abutment device.

Referring to the drawing, the engine or motor 1 may be of any suitable type of inboard motor and is mounted in the stern board of a boat by means of a resilient and watertight bushing 3 which surrounds a neck portion 4 provided around the substantially horizontal extension of the motor shaft. Outside the stern board 2 a gear case 5 is bolted to the motor assembly. The gear case contains a reduction gear, a reversing gear 22 and a bevel gearing 23 for transmitting the motor power to a vertical shaft 6 enclosed in a propeller housing 7 which near its lower end comprises a further bevel gearing 24 for transmitting the power to a propeller 8 on a horizontal shaft 25.

The propeller housing 7 is adapted to be turned relative to the gear case 5 and is connected to the rudder connection of the boat by means of a steering arm 9. The bevel gearing 23 in the gear case 5 is arranged such that the propeller housing 7 can be swung upside down, e.g., by means of a handle 26. To this end, the point of connection between the steering arm 9 and the rudder connection is located centrally with respect to the bevel gearing. In the swung-down position of the propeller housing 7 the thrust from the propeller 8 is taken due to the fact that the propeller housing via an abutment device bears on the stern board 2.

Due to the torque exerted by the shaft 6, the propeller housing 7 tends to turn away from the longitudinal center line of the boat. For this reason the abutment device is constructed to compensate for the action of the torque. Bolted or otherwise secured to the stern board 2 is a tubular case 10 in which a sleeve 11 is axially adjustable by means of a pin 12 which is inserted through one of a plurality of transverse holes 13 in the case 10 and through "ice a corresponding hole in the sleeve 11. Due to this arrangement the trim position of the propeller can be adjusted.

Inserted in the sleeve 11 is a rubber bushing 14 which surrounds another tubular sleeve 15. A journal 16 is rotatably mounted in the sleeve 15 by means of balls 17 which also take axial forces. Secured to the end of the journal extending outside the sleeve 15 is a supporting projection 18 which has a substantially vertical plane supporting surface 19.

On a level with the projection or abutment 18 a horizontal cam disc 20 is secured to the propeller housing 7. The side of the cam disc facing the abutment 18 is in the form of a cam profile 21 which may be an arc of a circle or a spiral 21a having its center laterally offset from the axis of the shaft 6 when the propeller housing 7 assumes its central position. In this position, the point of contact between the cam profile 21 or 21a and the abutment 18 will also be laterally offset from the center line of the propeller housing, as shown in FIGS. 2 and 2A, and a moment arm of the thrust from the propeller is obtained such that the moment of the thrust will counteract the above-named torque and tend to keep the propeller housing in its central position. By the expression lateral- 1y offset is here meant the relative disposition shown in FIGS. 2 and 2A, wherein a vertical plane through the centerline of the propeller shaft and a plane through the contact point and the center of the cam profile are parallel to, but offset from, each other so as to produce a moment arm counteracting the torque otherwise tending to turn the propeller housing. By adjustment of the cam disc 20 in different angular positions the length of the moment arm can be varied until complete balance is obtained.

Since the journal 16 and the abutment member 18 will be turned when the propeller housing is turned for steering the boat, the steering forces will be insignificant and the restoring torque can act without loss of power. Suitably, the axis of the journal 16 is laterally offset from the center line of the propeller housing at a distance equal to the required length of the moment arm.

What is claimed is:

1. A propeller mechanism for boats comprising a vertically extending housing suspended on the stern board of the boat, a propeller carried by said housing, a vertical driving shaft for said propeller, means for rotating said propeller including said vertical driving shaft in said housing, a horizontal shaft on which said propeller is mounted, a bevel gearing at the upper end of said driving shaft, means for turning said housing around the center of said bevel gearing about a vertical and a horizontal axis, an abutment on the stern board of the boat, and a horizontal cam disk on said housing, said abutment and cam disk, in all steering positions of the housing, cooperating laterally offset from the vertical driving shaft for taking up the thrust from the propeller in order to counteract torque developed on said housing by said propeller.

2. A propeller mechanism for boats comprising a vertically extending housing suspended on the stern board of the boat, a propeller carried by said housing, a vertical driving shaft for said propeller, means for rotating said propeller including said vertical driving shaft in said housing, a horizontal shaft on which said propeller is mounted, a bevel gearing at the upper end of said driving shaft, means for turning said housing around the center of said bevel gearing about a vertical and a horizontal axis, an abutment on the stern board of the boat, and a horizontal cam disk on said housing, said abutment and cam disk, in all steering positions of the housing cooperating laterally ofiset from the vertical driving shaft for taking up the thrust from the propeller in order to 3 1 counteract torque developed on said housing by said propeller, the invention being further characterized in that the profile of the cam is formed as an arc of a circle having its center laterally offset from the axis of the vertical driving shaft.

3. A propeller mechanism for boats comprising a vertically extending housing suspended on the stern board of the boat, a propeller carried by said housing, a vertical driving shaft for said propeller, means for rotating said propeller including said vertical driving shaft in said housing, a horizontal shaft on which said propeller is mounted, a bevel gearing at the upper end of said driving shaft, means for turning said housing around the center of said bevel gearing about a vertical and a horizontal axis, an abutment on the stern board of the boat, and a horizontal cam disk on said housing, said abutment and cam disk, in all steering positions of the housing cooperating laterally offset from the vertical driving shaft for taking up the thrust from the propeller in order to counteract torque developed on said housing by said propeller, the invention being further characterized. in that the profile of the cam is formed as an arc of a spiral having'its center laterally offset from the axis of the vertical driving shaft. 1

4. A propeller mechanism for boats comprising a vertically extending housing suspended on the stern board of the boat, apropeller carried by said housing, a vertical driving shaft for saidtpropeller, means for rotating said propeller including said vertical driving shaft in said housing, a horizontal shaft on which saidpropeller is mounted, a bevel gearing atthe upper end of said driving shaft, means for turning said housing around the center of said bevel gearing about a vertical and a horizontal axis, an abutment on the stern board of the boat, and a horizontal carn disk on said housing, said abutment and cam disk, in all steering positions of the housing cooperating laterally offset from the vertical driving shaft for taking up the thrust from the propeller in order to counteract torque developed on said housing by said propeller, the invention being further characterized in that said abutment comprises a projection having a vertical plane surface, and further comprising a horizontal journal attached ,to said projection, and a case attached to the stern board of the boat, said journal being rotatably mounted in said case. 1 1

5. A propeller mechanism for boats comprising a vertically extending housingsuspended on the stern board of the boat, a propeller carried by said'housing, a vertical driving shaft for said propeller, means for rotating said propeller including said vertical driving shaft in said housing, a horizontal shaft on which said propeller is mounted, a bevel gearing at the upper end of said driving shaft, means. for turning said housingraround the center of said bevel gearing about a vertical and a horizontal axis, an abutment on the stern board of the boat, and a horizontal cam disk on said housing, said abutment and cam disk, in all steering positions of the housing cooperating, laterally offset from the vertical driving shaft for taking up the thrust from the propeller in order to counteract'torque developed on said housing by said propeller, the invention being further characterized in that said abutment comprises a projection having a vertical plane surface, and further comprising a horizontal journal attached to said projection, and a case attached to the stern board of the'boat, said journal, being rotatably mountedin said case, and axially displaceable in' said case for adjusting the distance between the plane surface oftheprojection and said case.

' References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROPELLER MECHANISM FOR BOATS COMPRISING A VERTICALLY EXTENDING HOUSING SUSPENDED ON THE STERN BOARD OF THE BOAT, A PROPELLER CARRIED BY SAID HOUSING, A VERTICAL DRIVING SHAFT FOR SAID PROPELLER, MEANS FOR ROTATING SAID PROPELLER INCLUDING SAID VERTICAL DRIVING SHAFT IN SAID HOUSING, A HORIZONTAL SHAFT ON WHICH SAID PROPELLER IS MOUNTED, A BEVEL GEARING AT THE UPPER END OF SAID DRIVING SHAFT, MEANS FOR TURNING SAID HOUSING AROUND THE CENTER OF SAID BEVEL GEARING ABOUT A VERTICAL AND A HORIZONTAL AXIS, AN ABUTMENT ON THE STERN BAORD OF THE BOAT, AND A HORIZONTAL CAM DISK ON SAID HOUSING, SAID ABUTMENT AND CAM DISK, IN ALL STEERING POSITION OF THE HOUSING, CO- 